Does the GH2 Extended Tele Converter affect the video quality?

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M43photo made a very interesting Tele Converter test on the GH2 and 14-42mm lens. The ETC mode gives a tele conversion of 2.6x when recording 1080 lines in and 3.9x in 720 lines (Video mode).

As you can see from the image samples on the website: “It appears that the video stream recorded using ETC has worse image quality than the normal stream, at all ISO values. There is some lack of sharpness and contrast, and more noise in the ETC video streams.

M43photo explains the (little) quality loss with the fact that ETC recording doesn’t have the option of scaling down from a larger number of pixels (in normal recording mode the whole sensor area is used and scaled down).

I suggest you to make your own tests. Let us know if you can confirm the conclusions from m43photo! Thanks!

P:S.: GH2 direct links to Amazon, Olympus US store, Adorama, B&H, eBay.

UPDATE: A good friend of us (and very good tester) said:
The extender 2,6 function depends on the optic that is used. The Leica 45mm Macro[/shoplink] gives the same frame quality in extender mode as a HI Q optics. The same for 7- 14 mm. Both tested result! The 14- 42 is the weakest lenses in the Panasonic lens set. So the result can be right but the result is not easy to apply on other optics

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  • Zonkie

    ETC mode turns your big sensor camera into a small sensor camera (basically it turns a m4/3 camera into a camcorder). This means:

    – You no longer have a shallow depth of field (less so than in a digicam).
    – You no longer have good high ISO performance (idem).

    What you win is having no scaling artifacts (again, same as with a camcorder).

    As an option that comes for free it’s good to have ETC mode. But for the most part, who would buy a big sensor camera to turn it into a camcorder with worse ergonomics?

    • Steve

      I am surprise after all this time that ETC is still misunderstood. ETC has no impact on the DOF. DOF is based on the size of each sensor pixel, not the number of pixels. Also, while the high ISO performance is impacted due to no downconverting, it is still better than the small sensor camcorders and has not artifacts.

      • Ganec

        high ISO is not affected because current “big chip” cameras does not produce final image by downsizing whole image (*), but via ignoring most of the pixels

        (*) imagine whole image downsizing: if it worked, it must read whole 16 megapixels 30fps which is currently not possible => if it could, it will offer it for continuous shooting

        • http://m43photo.blogspot.com/ M43Photo

          I agree with your comments, and I’ve adjusted the article text to make it more clear.

        • http://www.flickr.com/photos/41967279@N05/ zebarnabe

          GH1 and GH2 make some sort of resize/pixel binning (on hardware, not firmware), aliasing artifacts are less like to occur as it happens with Canons 550D/7D or even 5D…

          Shot some fences or other pattern prone to aliasing troubles to test it (moire patterns are often a result of aliasing issues)… but yes, I believe some pixels are ignored (even more in GH2 as it has a bigger resolution), but it does a great job hiding it in the final result :]

          Since less information is used to create the final image, it’s only natural to obtain a certain degradation when using ETC, but as it is an optional extra it’s always good to have it and know what it can do.

      • Zonkie

        >I am surprise after all this time that ETC is still misunderstood.

        So am I.

        >ETC has no impact on the DOF

        Of course it does. For the *same FOV* you get much larger DOF than you would get in normal mode.

        For example, to get the same field of view as you would get with a 25mm focal length lens in normal mode, you have to use a 4.8mm focal length in ETC mode (same as with a digicam with a 1/2.3″ sensor). Since DOF depends on focal length, with the much shorter focal length you get a much larger DOF.

        >Also, while the high ISO performance is impacted due to no downconverting, it is still better than the small sensor camcorders and has not artifacts.

        It is not affected by downconverting, it is affected by having a much smaller surface to gather the light. You are using a 1/2.3″ inches sensor size in ETC mode. There are no miracles to be done with that. The performance is equivalent of a camcorder with a sensor that has similar quality (and yes, pixel size is also the same in a camcorder since both have around 2MP in the same area).

        But yes, it has no downscaling artifacts when compared to shooting in normal mode. Just as camcorders don’t have them either. Because there is no downscaling.

        • Zonkie

          Correction, to get the same field of view in ETC mode as you would get with a 25mm focal length in normal mode you’d have to use a focal length of 9.6mm, not 4.8.

        • El Aura

          > It [high ISO performance] is not affected by downconverting, it is affected by having a much smaller surface to gather the light.
          Well, you are not using the full surface of the sensor in normal video mode either. While there is some binning (usually in one direction), a lot of the pixels are skipped in video mode. Thus the active pixel area in video mode is already smaller by a factor of three (if for example only every third line of pixels is read) compared to still photography.

    • http://www.flickr.com/photos/miklosrabi Miklos Rabi

      Have you ever tried this?

      • Zonkie

        Nope, I don’t have a GH2. Why?

  • Tropical Yeti

    And of course – with such heavy cropping, optics performance becomes a problem too…

  • Miroslav

    “M43photo explains the (little) quality loss with the fact that ETC recording doesn’t have the option of scaling down from a larger number of pixels”

    Of course, if you scale 4976 x 2800 image to 1920 x 1080 in Photoshop, you’ll get sharper image with less noise than if you crop 1920 x 1080 from the center. Nevertheless, useful thing.

  • mpgxsvcd

    Testing ETC modes with a compressed youtube video is useless. You must do a controlled test with original files.

    You can download original ETC resolution chart samples for all GH2 formats in the link below.

    http://vimeo.com/user442745/videos/page:2/sort:newest

    My testing has shown that resolution wise the ETC shots are nearly identical to their non-ETC counter-parts. However, the magnification of the pixels does emphasize noise greatly. ETC is really only usable up to ISO 640.

    It is still very useful though. The 20mm turns into an F1.7 52mm lens in 1080p ETC mode. Even If you can only go up to ISO 640 the 20mm is still at least 3 stops brighter than any of the zoom lenses.

    • http://m43photo.blogspot.com/ M43Photo

      I wouldn’t say it’s completely useless, since in the youtube videos you can clearly see that there is more noise in ISO 640 ETC than ISO 640 normal.

      But in general, your comment is of course correct, and I added 100% crops from still images from each test to be able to compare better. Still, this is no scientic test.

      • mpgxsvcd

        I applaud your effort for doing this test. I agree it does show a difference in noise. However, it appears that the youtube compression is actually hiding a lot of the noise in the ISO 2500 ETC shot. The difference is even greater than what the video shows. The ETC mode straight out of the camera is very poor in the ISO 2500 range.

        I don’t think you can draw any conclusions about resolution from looking at a youtube clip. The compression in the streaming video does much more to affect resolution than the ETC mode does.

        • http://www.flickr.com/photos/41967279@N05/ zebarnabe

          +1 yep … Youtube compression eats most of noise and fine patterns …

    • Miroslav

      “20mm turns into an F1.7 52mm lens in 1080p ETC mode. Even If you can only go up to ISO 640 the 20mm is still at least 3 stops brighter than any of the zoom lenses.”

      When the megapixel count increases to something not necessary at all, + 20mpx for example, YMMV, I hope manufacturers will completely replace kit zooms with this kind of in-camera cropping for stills, not only for video. This test shows how much image quality suffers. Yes, Panasonic cameras ( and some other P&S ) already have this feature, but it’s not implemented good enough IMHO…

      • mpgxsvcd

        ETC mode does nothing for stills. You are much better cropping in post processing no matter how many megapixels the sensor is.

        • Zonkie

          True. Actually ETC mode has been available in every stills camera on the market ever since. It is better known as cropping, and some manufacturers made it available in camera and called it “digital zoom”. No one ever cared about it, so nowadays it has disappeared as far as I know.

          • Miroslav

            No, digital zoom is not the same as ETC. With digital zoom camera crops AND enlarges the cropped part to native resolution, which is of course useless.

            Yes, you can crop in post process, but if that on-the-fly cropping saves you time, then why not? And I’m talking about very useful 3000 x 2250 pixel crops ( for example ), not 640 x 480.

        • http://m43photo.blogspot.com/ M43Photo

          Perhaps one exception to this is that when using digital zoom, you get some help from the camera in framing, autofocus, and metering.

          If you crop in post process, you risk that the camera’s automatic focus and metering is confused by what’s outside your intended crop. So using digital zoom could have some merit also for stills.

          But in principle, you’re right that digital zoom has little use for stills.

        • El Aura

          > much better?
          Cropping in post or during capture yields exactly the same result from an IQ point of view. You are using exactly the same pixels.

          Of course, you have the freedom to move the crop when you crop during post but that is about it. And for cropping in camera in main advantage is smaller file sizes (plus the already mentioned expectation of the AF and exposure are better targeted).

    • Zonkie

      Yes, the 20mm F1.7 turns into 52mm and keeps the F1.7. For shooting in low light if you need that focal length it’s good. But regarding control over DOF it’s not that good.

      Translating to full frame terms, the 20 F1.7 becomes a 40mm F3.4 (FOV and DOF) when used in normal mode. In ETC mode it turns into a 104mm F8.8. To match that in normal mode (on the GH2), you’d need a 52mm F4.4. That’s worse than what you can get with the 45-200mm F4.0-5.6 zoom.

  • mpgxsvcd

    Here is a better real world sample.

    http://vimeo.com/20632263

  • Jm

    While images quality may take a hit, mostly at higher ISO values, something made quite plain in this video (and which has been ignored until now) is the effect of ETC on traffic quality. With ETC turned on, traffic on the left side of the frame begins to suffer almost immediately. This is not surprising given the fact that a smaller portion of the sensor is utilized, which would reduce the number of cars that fit in a frame.

    What is puzzling is that there is an increase in traffic at ISO2500 EVEN WITHOUT ETC! I’m at a loss to explain the cause for this.

    • G_C

      indeed… i think small sensor cameras cause traffic jams!

      no wonder… since digital p&s’s came out my highways have been packed!

      thanks Jm!

  • twoomy

    ETC mode slows down traffic in the exit lane.

    • Fish

      Ha! That was good.

  • http://www.43rumors.com/members/hacky/ Helge Hackbarth

    In this sample http://www.youtube.com/watch?v=DOWDavMHGBY is a sequence starting from 2 min 25 sec, where the scenery under low light (High ISO) conditions is switched between normal and ETC mode.

    It is obvious that the image quality degrades in ETC under these conditions. Especially the noise becomes more visible in ETC. I am quite sure that in normal mode the downscaling takes also dropped pixels into account in order to achieve a better image quality.

  • http://www.peterdv.com Peter J. DeCrescenzo

    I own a GH2 & GH1 (w. “GH13” firmware hack). Apologies in advance for this long post …

    Concerning the GH2’s Extra Tele Conversion (EX) sensor crop mode feature, which is only available for video:

    – ETC’s only negative effect on video quality is a relatively small worsening of video S/N performance. In actual use, at ISO values under 640 or 800 or so the added noise can be quite acceptable, especially if no other alternative was available. Sure, mounting a fast, longer focal length lens would be preferable because there’d be no increase in video noise. But if such a lens is not at hand, at the mere press of a button, ETC can be an acceptable substitute, depending on ones circumstances.

    For example, here’s a link to a video clip I shot at ISO 1250. Its video quality is quite acceptable for many applications. This was one of the first times I’d used my GH2 or ETC. In hindsight, the video might look slightly less noisy if I had instead used ISO 1600 (on the GH2, ISO 1600 can be cleaner than 1250). Vimeo members can download the camera-original .MTS file:
    http://vimeo.com/18001992

    – ETC’s advantages: In addition to sometimes saving the expense of owning/renting a longer lens (or having to switch lenses in rainy, dusty or fast-changing conditions), ETC has other important advantages. ETC has _no_ affect on exposure. ETC video has markedly less alias & moire artifacts compared to the GH2’s non-ETC modes. ETC video has markedly less rolling shutter artifacts (“skew” & “jello”).

    – ETC mode has obvious advantages in shooting video which benefit from higher magnification, such as wildlife, sports, and so forth. This combined with ETC’s reduced rolling shutter & other artifacts can be a huge win when used appropriately. Plus, this added magnification involves no increase of kit weight, size or cost and can be switched on/off instantly between takes. True, there can be an increase of noise at higher ISO settings, but that’s the only disadvantage.

    – ETC of course works with any lens that can be mounted on a GH2 m43 camera, including lenses with relatively small image circles (such as most c-mount, 2/3″ and 1/2″ lenses) without vignetting. Since only the middle portion of the sensor is used, lenses with quite small image circles can yield great results. And, with all lenses, video shot in ETC mode benefits from using the middle area of the lens, usually the sharpest part of the lens with the fewest optical artifacts.

    – ETC and DOF: When the GH2 switches between normal (non-ETC) mode and ETC mode, the DOF in the scene does not change. The full res image captured by the sensor is cropped to the middle 1920 x 1080 pixels (when recording HD). Of course, this may not be what the audience expects. They may have expected the DOF to change when the apparent focal length changed, but in fact only the image cropping changed. There is no “free lunch”. If you want your audience to see certain DOF characteristics, use the optics and exposure settings required to produce that result.

    Like any other tool, ETC can be very useful in certain situations, and it has important benefits as described above. But ETC is not necessarily a substitute for using a long, fast lens — especially when the lowest possible noise or “normal” DOF characteristics are required.

    Cheers.

    • Zonkie

      >ETC and DOF: When the GH2 switches between normal (non-ETC) mode and ETC mode, the DOF in the scene does not change.

      The DOF does not change indeed, but the field of view (FOV) does change! And that’s the point that people are not getting. If you shoot a portrait in normal mode at 50mm F2.0 you get a certain DOF. Now if you change to ETC mode you do get the same DOF, but instead of a portrait you will get a macro shot of a nose. So to have a portrait you would have to step back a few meters. Then you would get the same FOV, but a much larger DOF.

      In ETC mode the DOF is *exactly* the same as with a camcorder (for the same FOV).

      I don’t say it is useless. It is useful. But let’s face it, you buy a big sensor to get shallow DOF and good low light capabilities. in ETC mode you lose both (and you gain in less artifacts). Same as if you used a camcorder instead.

  • http://benbunchfilms.com Ben

    I have a couple shots in a new narrative short I did with the GH2 (will be online within the next few days will link it to you.) It has a few ETC shots in it and I noticed a marked difference in quality…mainly they’re noisier and more contrasty. That said it varies best on lenses used and lighting conditions.

  • Wolf

    A question from a new owner of a GH1.
    Is the GH2 ETC feature a hardware or a Firmware/Software function?
    I know it is basically only a crop function but would be nice if it could be implemented on a GH13 as well.

  • Koldo

    For the video quality, it is also important the aperture. There is more noise in f22 than in f8. Tested.

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